Systems including optical interconnect devices are often used to transmit information at high data rates. For example, such systems are used for board-to-board, backplane, local area network (LAN), wide area network (WAN) and similar applications. Optical systems have advantages when compared to electrical interconnect systems. Optical systems are generally less susceptible to electromagnetic interference resulting in increased transfer efficiencies.
Short reach (<2 meters) optical interconnects for chip-to-chip and board-to-board optical communications have been under development for more than 10 years, primarily funded by the US Department of Defense. The need for these optical interconnects is driven by the bandwidth, security, reliability, and size requirements of the next (and future) generation computers and telecommunication systems. With internal clock speeds approaching 3 GHz today and projected to be 5 GHz in the next few years, the bottleneck limiting the speed of future computer systems is the data transfer step from a source computer processor chip and routed to other computer processors, DSPs, and data storage devices at equivalent or higher data rates than the clock speed.
There have been many technologies developed to solve this interconnect bottleneck, including optical interconnects. Typical optical interconnect systems generally include a light emitting device, such as a laser transmitter and a light detecting device, such as a photodiode linked by a waveguide material. Costs associated with the production of optical interconnect systems are high due to the complex manufacturing methods utilized. There is therefore a need in the art for a cost effective method of fabricating a waveguide optical light path, or optical link, that will guide light from the transmitter to the receiver that can be embedded into a standard printed wiring board (PWB) fabrication process, or embedded into a flex circuit.
There is a need for a multimode optical link that can connect any two points on the surface of a substrate, preferably a printed wiring board (PWB). Such an optical link requires a fabrication process for multi mode polymer waveguides that can be cost effectively scaled to large area substrates, including glass and a variety of rigid and flexible PWB board compositions, such as glass fiber-resin (FR4) and polyimide. The multimode waveguides are then combined with out-of-plane mirrors to create the optical link. Several different techniques have been used in the past to fabricate out-of-plane mirrors in polymer waveguides including laser ablation, reactive ion etching (RIE), a microtome process, molding, and glass insertion devices. All of these previous techniques have either required costly tools to implement the process, or created mirrors with high loss such that the techniques could not be applied to a commercially viable process. The out-of-plane mirrors and waveguide should be robust enough to survive the temperature, pressure, and chemical environment required by the PWB fabrication process.